That view comes from Stifel Nicolaus analysts Jordan Rohan and Michael Purcell, who boosted their price target on the social network to $50 from $38. The analysts on Friday cited Facebook’s surprisingly strong second-quarter results, released last month, as a key turning point for the company and a catalyst for their increasingly optimistic views.

“It seems highly likely that the earnings results from the second quarter are not an isolated flash of brilliance,” Stifel says. “We believe the upside will last at least a year, perhaps longer.”

Shares recently rose 0.4% to $41.46. The stock is up more than 55% since Facebook’s quarterly report was released on July 24.

Stifel isn’t letting the huge rally in such a short time frame deter its rosy views. “While we have raised estimates, we believe our new estimates remain conservative on both margins and revenues,” the firm says. “Accordingly, we believe the likelihood of significant earnings upside is high.”

Facebook shares traded as high as $45 on May 18, 2012, the day the company went public. For more than a year, the social network hadn’t come close to sniffing that level. But over the past month the rally has shown few signs of letting up; shares traded as high as $42.26 earlier Friday.

Stifel is optimistic the rally will continue as long as Facebook keeps gaining advertising market share. “In our experience, companies undergoing inflections in online advertising businesses are likely to continue to do so for a few quarters, if not years,” the firm said.

The Stifel analysts cite several examples backing up their thesis. From Stifel:

Netscape’s moment in the sun was somewhat brief, all things considered, ultimately losing a browser war to Microsoft. Even still, there were several quarters of upside after the 1995 IPO.

AOL Inc. held onto its position of dominance for a couple years, long enough to negotiate a merger with Time Warner in 2000, but its position of dominance was tied to narrowband access.

Yahoo Inc. had two periods of leadership, a late-90s period driven by sponsorship deals and venture capital dollars and a more sober search-based business model driving the upside from 2002 through 2006. Arguably, the investment in Alibaba is giving the stock, but not the earnings from the consolidated operations, a third period of ascendance.

Google Inc. enjoyed a period of near-infallibility for a solid 2-3 years after its IPO, until the economy fizzled in 2008. When Android began to outsell Apple devices, globally, by a wide margin, investors gave Google another look. But the second period of stock upside has been driven mostly by multiple expansion, not earnings upside.

Assuming Facebook’s results weren’t a fluke, Stifel says Facebook bulls could still have more to cheer.

“The stock call at this level depends on earnings momentum — as long as the company continues to outpace consensus estimates for revenue growth, with high incremental margins, shares should continue to climb,” Stifel says.